About 15 years ago I was given this Power Transformer that is unidentified by me. I remember being told by Jeff Snider that it belonged to a Marshall dual monobloc rack mount power amp. I googled pictures of those and it wasn't out of the gold/newish ones. If anything, it was out of my old Marshall Series 9000 50/50 rack mount power amp.

Here are the pics:

And here are the readings I got from testing every lead against itself:

What I want to know is:
1) What is the blue wire? Most Marshall stuff shows it as common.
2) What are the orange wires for?
3) I know that the greens are 6.3vac heaters
4) Reds are HT
5) I think yellow is rectifier 5v (no way to tell until I test voltages from it)

If I were to apply voltage to it, I assume black goes to one side of a power cord and the black/white goes to the otherside. Where does ground go to?